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Activity Under Equity Incentive Plans Related to Stock Options (Detail) - 2008 Equity Incentive Plan shares in Thousands	9 Months Ended
	Sep. 30, 2020 $ / shares shares
Activity under the Company's equity incentive plans related to stock options
Number of Options Outstanding, Beginning Balance | shares	16,830
Granted, Number of Options Outstanding | shares	2,237
Exercised, Number of Options Outstanding | shares	(1,581)
Forfeited/canceled, Number of Options Outstanding | shares	(78)
Number of Options Outstanding, Ending Balance | shares	17,408
Weighted Average Exercise Price per Share
Weighted Average Exercise Price per Share, Beginning Balance | $ / shares	$ 4.53
Granted, Weighted Average Exercise Price per Share | $ / shares	5.22
Exercised, Weighted Average Exercise Price per Share | $ / shares	3.72
Forfeited/canceled, Weighted Average Exercise Price per Share | $ / shares	5.29
Weighted Average Exercise Price per Share, Ending Balance | $ / shares	$ 4.69

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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